Embodiments of the inventive concept relate to semiconductor devices and, more particularly, to image sensors, image processing systems and methods of operating the same.
Image sensors are devices that convert an optical image into an electrical signal. Image sensors include charge coupled device (CCD) image sensors and complementary metal-oxide-semiconductor (CMOS) image sensors.
A CMOS image sensor (or a CMOS image sensor chip) may be described as an active pixel sensor manufactured using CMOS semiconductor processes. A typical CMOS image sensor includes a pixel array including a plurality of pixels. Each of the pixels includes a photoelectric conversion element that converts an optical signal into an analog electrical signal and an additional circuit that converts the analog electrical signal into a digital signal.
A typical CMOS image sensor may include, for example, analog to digital converter (ADC) circuitry configured to convert pixel signals into multi-bit digital codes, which may be stored in memory. The store digital codes may be transferred from the memory to a data bus in a bit by bit manner. For example, in response to a first address, a first bit of a first digital code corresponding to a first pixel may be transferred to the data bus, in response to a second address, a first bit of a second digital code corresponding to a second pixel may be transferred to the data bus, in response to a third address, a first bit of a third digital code may be transferred to the data bus, and so on.
The number of pixels, the resolution of an analog-to-digital converter, and a high frame rate are important factors that determine the quality of images processed by the CMOS image sensor. These factors may correlate with the data transfer efficiency of the data bus.
Data bus frequency may be increased in order to increase the data transfer efficiency of the data bus. However, when the data bus frequency increases, there may be a problem in restoring data in a receiver due to interference during data transmission. In addition, when the resolution of the analog-to-digital converter circuitry is increased and a multi-channel data bus is used, more silicon area may be required to form the analog-to-digital converter and the multi-channel data bus. As a result, the die size of the CMOS image sensor chip may increase. Therefore, the die size may need to be reduced by decreasing the silicon area in order to increase gross die or net die. Here, gross die or net die may be defined as the number of semiconductor chips that can be formed in a single wafer.